Add pluck method

lib/dynamoid/criteria.rb

@@ -8,7 +8,7 @@ module Criteria
  extend ActiveSupport::Concern
 
  module ClassMethods
- %i[where all first last each record_limit scan_limit batch start scan_index_forward find_by_pages project].each do |meth|
+ %i[where all first last each record_limit scan_limit batch start scan_index_forward find_by_pages project pluck].each do |meth|
  # Return a criteria chain in response to a method that will begin or end a chain. For more information,
  # see Dynamoid::Criteria::Chain.
  #

lib/dynamoid/criteria/chain.rb

@@ -164,6 +164,20 @@ def project(*fields)
  self
  end
 
+ def pluck(*args)
+ fields = args.map(&:to_sym)
+ @project = fields
+
+ if fields.many?
+ items.map do |item|
+ fields.map { |key| Undumping.undump_field(item[key], source.attributes[key]) }
+ end.to_a
+ else
+ key = fields.first
+ items.map { |item| Undumping.undump_field(item[key], source.attributes[key]) }.to_a
+ end
+ end
+
  private
 
  # The actual records referenced by the association.
@@ -172,7 +186,12 @@ def project(*fields)
  #
  # @since 0.2.0
  def records
- pages.lazy.flat_map { |i| i }
+ pages.lazy.flat_map { |items, _| items }
+ end
+
+ # Raw items like they are stored before type casting
+ def items
+ raw_pages.lazy.flat_map { |items, _| items }
  end
 
  # Arrays of records, sized based on the actual pages produced by DynamoDB
@@ -181,11 +200,19 @@ def records
  #
  # @since 3.1.0
  def pages
+ raw_pages.lazy.map do |items, options|
+ models = items.map { |i| source.from_database(i) }
+ [models, options]
+ end.each
+ end
+
+ # Pages of items before type casting
+ def raw_pages
  if @key_fields_detector.key_present?
- pages_via_query
+ raw_pages_via_query
  else
  issue_scan_warning if Dynamoid::Config.warn_on_scan && query.present?
- pages_via_scan
+ raw_pages_via_scan
  end
  end
 
@@ -194,13 +221,12 @@ def pages
  # @return [Enumerator] an iterator of the found pages. An array of records
  #
  # @since 3.1.0
- def pages_via_query
+ def raw_pages_via_query
  Enumerator.new do |y|
  Dynamoid.adapter.query(source.table_name, range_query).each do |items, metadata|
- page = items.map { |h| source.from_database(h) }
  options = metadata.slice(:last_evaluated_key)
 
- y.yield page, options
+ y.yield items, options
  end
  end
  end
@@ -210,13 +236,12 @@ def pages_via_query
  # @return [Enumerator] an iterator of the found pages. An array of records
  #
  # @since 3.1.0
- def pages_via_scan
+ def raw_pages_via_scan
  Enumerator.new do |y|
  Dynamoid.adapter.scan(source.table_name, scan_query, scan_opts).each do |items, metadata|
- page = items.map { |h| source.from_database(h) }
  options = metadata.slice(:last_evaluated_key)
 
- y.yield page, options
+ y.yield items, options
  end
  end
  end